Annabeth is also highly popular. Her intelligence and relationship with Percy add a lot of depth to the stories. In fanfiction, she can be involved in solving complex puzzles or leading her own quests.
The gods are also very popular characters to include. For example, Poseidon as Percy's father always brings an interesting dynamic. His power and the relationship between father and son can be explored in many different ways in fanfiction.
Obviously, Percy Jackson himself. He's the main character of the original series, so having him interact with the SI character can create many exciting storylines.
Grover can be a great addition. His ability to sense danger and his connection to nature can be translated into some unique in - game abilities. Also, Nico di Angelo is quite popular. His control over the dead could be a very cool power - up or special ability in the fanfiction's gaming world.
Percy himself is obviously a very popular character to include since the whole concept of tg (transformation) can be applied to him in many different and interesting ways. His friends like Annabeth are also popular. You can create scenarios where Annabeth has to deal with Percy's transformation and how it affects their relationship.
Aside from Percy, Jason Grace is often included. He has his own set of powers and experiences from being a Roman demigod, which can create great conflicts and alliances in fanfiction. Piper McLean is also a great character to add. Her charm - speak ability can be used in really creative ways in a story. And of course, Leo Valdez with his mechanical skills and humorous personality can add a lot of fun and action to the fanfiction.
Percy Jackson himself is obviously very popular. He's the main character in the original series and in many fanfictions, his growth and new adventures are central. Another popular character is Annabeth. Her intelligence and strategic thinking often play important roles in the battle - related fanfictions. Also, Ares, as the god of war, is often a key figure in these stories.
Percy himself is obviously very popular. After all, it's his series. Annabeth is also a fan favorite, as her intelligence and strong will make for interesting storylines. Nico di Angelo is quite popular too, especially when his powers and his somewhat dark nature are explored in fanfiction.
There are also some minor gods that might be popular in these fanfictions. For example, Hermes, the messenger god. His ability to move quickly and his knack for getting into and out of trouble could be used to further the plot in stories involving Percy and Artemis. His role as a bit of a trickster can also add some humor and unpredictability to the fanfiction.
One of the most interesting characters to include would be Hermione from Harry Potter. Her intelligence and knowledge of magic could help Percy and his friends in many situations. Also, Captain America from the Avengers. His leadership and sense of justice would blend well with Percy's own heroic nature. And Clary from the Mortal Instruments, her skills as a shadowhunter and Percy's demigod abilities could create a really engaging story.
Jason Grace is often included. His leadership skills and ability to fly would be useful in various crossovers. In a crossover with the X - Men, he could be seen as a mutant with his flying and lightning powers. Piper McLean is also a favorite. Her charm - speak ability could be very effective in different crossovers. For instance, in a crossover with the world of Game of Thrones, she could use it to manipulate some of the power - hungry lords. And let's not forget Grover. His satyr nature and his loyalty to Percy make him a great addition to any crossover.
Grover is a great character to include too. His connection to nature and his loyalty to Percy make him a wonderful addition. He can provide comic relief at times, but also be a crucial part of the team when it comes to using his nature - based powers to sense danger or find hidden paths.